GT4 and Brakes

  • Thread starter Scaff
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.Duck.
1. How do you figure the weight distribution of the Vantage?

Got the Vantage static distribution from one of my big collection of car & motorsport books (currently just over 150), but I also find google a very good source.

.Duck.
2. What do you use/do to calculate the braking distance?

I use the data logger on the test track, the very long straights allow a total of six tests to be run in a single lap (100-0), switch off throttle in the data logger and ensure that speed is set to kmh (changes data logger fields to metres).

You can then get the start and end distances of each test from the data logger and calculate the braking distance.

.Duck.
3. Could you try setting the Brake balance to 3 / 5, and see what it does? And then 5 / 5 after that?

I will try and give them a go as soon as I can.

.Duck.
Sorry for asking so much. :indiff:

Not a problem Duck, I'm just glad this stuff is of interest.


sucahyo
Interesting, in GT2 all car have BBC defaulted to 12/12. Maybe because of this the time is different on more car.

2.2 meters is significant! I think I have to take the car weight distribution more seriously!. if I don't know the car weight distribution maybe I'll try brake tuning based on smoke and sound..............

2.2 metres is a very significant time difference, it one of the reasons I do so much work on brake settings


sucahyo
I shouldn't ignore the rules, that race brake need to be warmup..........

Do you need to warmup the racing brake in GT4?

The racing brakes in GT4 appear to have no effect on stopping distances, in fact no one who has tested them have found a measurable difference.

Have a look at the tests links on my first post.


Uncle Harry
Can you do some tests to check benifits around the track. When I race I dont need to come to a full stop. The extra stopping distance may be minor when the better stability in the turn in is factored in to the total lap time.

Very true, however it is a much more difficult area to measure, as pure lap times are subject to many factors beside braking. Driving style will also make a big difference to this, as producing very consistent laps for each setting can be difficult.

The advantage of a 100-0 test is that it is measureable in a consistent manner and allows cars to be compared easily.


Regards

Scaff
 
I am sorry everyone, it seems that I am wrong about warmup brake, because when I test the car again timing 195 to 120 mph braking, I found that using race brake have consistent time on each half lap. So the initial high braking time on previous test may be just concidence.
So, on my next test I will brake to the speed that will not locked the wheel.

About the race brake in GT2, it only has marginal change in braking time using race brake (I test it on 4 car, 3 increase, 1 decrease).

Lexus SC 300, 170 to 70, 170 to 0 mph data.
stock1 = 2.924 = 5.832
stock2 = 2.924 = 5.695
stock3 = 2.942 = 6.176
stock4 = 2.924
stock5 = 2.977
racing1 = 2.958 = 5.969
racing2 = 2.977 = 6.073
racing3 = 2.977 = 5.867
racing4 = 2.958 = 5.901
racing5 = 2.958 = 6.021
racing6 = 2.976
Race brake is marginally slower
It seems using 170 to 0 mph data is a bit unreliable.

V8 Vantage, 195 to 120, 195 to 0 mph data.
stock1 = 2.013 = 6.537
stock2 = 2.03 = 6.434
racing1 = 1.996 = 6.762
racing2 = 1.995 = 6.726
On the previous test, braking is done before the first corner, this test done after.
Race brake is little faster on 190 to 120, little slower on 195 to 0
195 to 0 mph data is also a bit unreliable.
 
.Duck.
Could you try setting the Brake balance to 3 / 5, and see what it does? And then 5 / 5 after that?

Duck I have completed the tests you requested and put the results in with the original results above, short piece on the results can be found at he bottom of that posted.

Regards

Scaff
 
Tyre vs Weight Reduction - Which stops you better

Following a discussion on the effects of weight on stopping distances (over in the GT2 forum) I have put this to the test in GT4.

Taking the Aston Martin Vantage '99 from the last set of tests, I ran the car in stops from 100mph to 0mph, with S3 tyres and then on N2 tyres with each of the three weight reduction stages.

The cars stock weight is 1970 kilos, each weight reduction looks at the total weight saving from this figure).

The brake bias setting was at the default of 3 / 3, to ensure the playing field was level for each run.

Results

Stock (from previous test) - 85m

Stock w/bbc set to 5/3 (from previous test) - 82.8m

S3 tyres (stock weight) - 70.2m
cost = 7,400

Weight Reduction 1 - 84.2m
(to 1733 kilos = 12% reduction from stock)
cost = 1,300

Weight Reduction 1+2 - 83m
(to 1674 kilos = 15% reduction from stock)
cost = 1,300 + 5,700 = 7,000

Weight Reduction 1 + 2 + 3 - 82.2m
(to 1635 kilos = 17% reduction from stock)
cost = 1,300 + 5,700 + 23,000 = 30,000


Conclusion

Quite clearly the biggest gain was made by fitting S3 tyres to a totaly stock car, it reduced the stopping distance by 14.8m or 17.4%. Value for money wise, its a cost of 500cr per metre.

The weight reduction stages did give a reduction in stopping distances, but as in the real world its not a major effect, with the following figures:

WR1
Reduction of 0.8m or 1%
CPM = 1,625cr

WR 1+2
Reduction of 2m or 2.4%
CPM = 3,500cr

WR 1+2+3
Reduction of 2.8m or 3.3%
CPM = 10,714cr

Brake Bias setting (5/3)
Reduction of 2.2m or 2.6%
CPM = Your time to set it.


Now its should be remembered that the distances from the Weight Reduction stages could be brought down further with brake bias settings, as the amount of weight transfering is reduced as the weight is reduced.

Now the results above are only applicable to the car tested, the results for different makes and models would vary. However I would expect a similar trend to remain. What he above does, quite clearly show is that tyres (as I have always maintained) have a far bigger impact on the stopping distance of a car than either weight or weight distribution.

However, thats not to say that you should never use weight reduction, just that it is not the best tool for reducing your braking distances. The main benifits from a reduced weight are in acceleration, due to a better power to weight ratio and cornering speeds, due to a lower PMI.

One again I hope that the above is of interest.

Regards

Scaff
 
Scaff
Duck I have completed the tests you requested and put the results in with the original results above, short piece on the results can be found at he bottom of that posted.

Regards

Scaff
Thanks!! I appreciate it! :D
 
Scaff
The racing brakes in GT4 appear to have no effect on stopping distances, in fact no one who has tested them have found a measurable difference.
I post my stock vs racing brake test in GT2 forum. racing brake can make braking faster in GT2.
 
sucahyo
I post my stock vs racing brake test in GT2 forum. racing brake can make braking faster in GT2.

Your results seem to indicate that racing brakes have more of an effect below 100mph.

I must find the time to take a look at this again in GT4, still it would not surprise me if racing brakes did not effect stopping distances. As if the stock brakes on a car are already sufficent, fitting bigger discs and better pads does not stop you quicker (in the real world).

Regards

Scaff
 
New GT4 vs Autocar 0-100-0 test.

Kent mentioned in a thread over in the main forum that he believes the brakes on the Zonda to be poor, having never tested one in GT4 (or unfortunatly the real world) I dug out some figures from the Autocar 0-100-0 test from 2003 which featured the Pagani Zonda C12S 7.3 '02, and ran the same test in GT to have a quick look.

In addition to the 0-100-0 test I also got the 60-0 figure from the original roadtest of the car, just to see how that shapes up.

The conditions for the test were the same as the previous ones for the Ford GT, M5 and Viper. Six runs best overall time taken for both the 0-100-0 and 60-0 runs.

0-30

Autocar = 1.84
N2 = 2.18
N3 = 1.88

The mid-engined layout helps with getting off the line, but the hugh power of the car wants to spin the tyres constantly, very balanced throttle control needed all the way to 30.

Both GT4 figures are very clos here, with the N3s being only 0.04 seconds adrift.


0-60

Autocar = 3.74
N2 = 4.94
N3 = 3.76

The Zonda is capable of 60 mph in first gear, but only just, you need to be into the red-line to get it. The N2 time was from the fastest overall run, but I changed gear just before 60, hence the reason this figureis out.

The N3 time is now to within 0.02 seconds of the Autocar test figure.


0-100

Autocar = 7.52
N2 = 8.24
N3 = 7.44

100 mph can be achieved in 2nd gear, which again helps keep the figures down. The N2 figure is now down by 0.72 seconds, while the N3 figure is ahead by 0.08 seconds.


Reaction Time

Autocar = 0.27
N2 = 0.22
N3 = 0.24


100-0

Autocar = 4.05
N2 = 4.14
N3 = 4.2

Both figures are within 0.15 seconds of the Autocar test, these figures also throw up the one issue with multiple runs and taking the overall quickst time. The quickest overall time was down to some very quick reactions on the brakes and was also the best 100-0 figure for those tyres.

The N3 time, while not poor, was from an excellent launch which resulted in a great run, however the braking was one of the slowest from the N3 runs, the quickest N3 100-0 time was 4.10.


Overall

Autocar 11.84
N2 = 12.60
N3 = 11.88

The N2 overall time was within 0.76 seconds, which is very respectable in its own right, particulalry the 100-0 time; however the N3 time was 0.04 seconds adrift which is quite frankly amazing. Nail the braking (which in theory could gain 0.1 seconds from my best 100-0 figure) and this time would be on the money.

To remove the human element I also look at he overall figures without the reaction time in place.

Autocar = 11.57
N2 = 12.38
N3 = 11.62

Still very close, with the N2 within 0.81 seconds and the N3 within 0.05 seconds.


60-0

The final test was from the Autocar roadtest on the C12S.

Autocar = 2.7
N2 = 3.22
N3 = 2.84

The N2 time here is adrift, by 0.52 seconds, however the N3 time is out by only 0.14 seconds.


Conclusion

The first one is that the closest tyres to 'real' in terms of stright line acceleration and deceleration are the N3's, also that with these fitted the GT4 Zonda is very, very close to its real world version.

I did run a quick couple of laps around the Grand Valley Speedway just to see how it handled on the track, with the N3 tyres fitted.

This was quite telling, as the car has the same issue as the Ford GT. Nothing wrong with the brakes, the car is just stupidly powerful and capable of amazing acceleration. Which leads to very high corner approach speeds that require earlier braking distances.

A good example of this is the final sweeper through the tunnel at GVS, this can be taken at approx 75 mph on N3 tyres, if you wait until you are actually in the tunnel (just with the Zonda) you're approach speed is around 120-130 mph. Sheading 55mph in that short a distance and setting the car for the corner is just not going to happen. The cars speed requires you to brake earlier, or fit much stickier rubber.

Regards

Scaff


BTW figures added to the 0-100-0 database found here
 
.Duck.
That's very interesting, Scaff. It's one of those cars that don't give you a sensation of speed in the game. 👍 👍

Good job.

Thanks Duck.

Yep is one of the cars to fall victim to the lack of sensation of speed, results in corner approach speeds that are far fastr than you realise.

Regards

Scaff
 
One more question about the brake balance controller that has been bugging me for a long time: are 3/3 brakes three times more powerful than the 1/1 and so on? I quess not, but what kind of scale are the power settings based on?
 
Greycap
One more question about the brake balance controller that has been bugging me for a long time: are 3/3 brakes three times more powerful than the 1/1 and so on? I quess not, but what kind of scale are the power settings based on?

A very, very good question and one that I can only guess at.

I would agree that its unlikely that 3/3 is three times stronger than 1/1, but how the scale itself works I have tried to fgure out a few times.

The other 'issue' is that it seems to vary from car to car, even with similar layouts, weight, etc.

Still not sure how this one could be figured out, I will give it some more thought and sorry I could not shed any more light on it.

Regards

Scaff
 
Scaff
Conclusion

The first one is that the closest tyres to 'real' in terms of stright line acceleration and deceleration are the N3's, also that with these fitted the GT4 Zonda is very, very close to its real world version.
Awesome ! big 👍 for six time on each test.
 
I have some question about stock vs racing brake test:
- did the test done on the stickiest tire?
- on what speed the tire start to smoke? and which tire, front or rear?
 
sucahyo
I have some question about stock vs racing brake test:
- did the test done on the stickiest tire?
- on what speed the tire start to smoke? and which tire, front or rear?

All my tests on stock vs racing brakes were done on either N2 or N3 tyres, which are the GT4 versions of simulation tyres (GT4 has 3 tyres of 'real' tyre).

These are far from the stickiest tyres in GT4, but I have not yet had a chance to test all of the tyres in GT4 is this way, as we now have 11 different types of road tyre (3 Normal, 3 Sport and 5 Racing) with dirt and snow tyres as well.

In regard to your second point I must confess I can't remember which tyre(s) locked up first, some of these tests were carried out quite a while ago now.

Regards

Scaff
 
Scaff
All my tests on stock vs racing brakes were done on either N2 or N3 tyres, which are the GT4 versions of simulation tyres (GT4 has 3 tyres of 'real' tyre).
From what you know, which tire should give the most effect when using different brake (stock vs racing)? simulation or racing tire?
 
sucahyo
From what you know, which tire should give the most effect when using different brake (stock vs racing)? simulation or racing tire?

I'm at work at the moment so I don't have my testing notes on me at present, but I can't recall that the tyre fitted makes a difference to the type of brake used.

I will give this one a go, will try braking with different types of tyre, with and without brakes fitted.

In reality the fittment of uprated brakes would on shorten stopping distances if the stock brakes were not up to the job. This has more chance of occuring with tyres with more grip, as they will ask more of the stock brakes.

So if racing brakes are going to show a benefit to stopping distances its going to be with racing tyres and the stickier/softer the better.

Hope to get a chance to have a look at this tonight, but I will post the results as soon as I can.

Regards

Scaff
 
Right a new set of tests for the Racing Brakes upgrade.

All previous tests on this upgrade has failed to show any effect at all on stopping distances, which would have basis in reality, as under most conditions the tyre would be the limiting factor on stopping distances and as long as the standard brakes were sufficent to exceed the tyres grip level then bigger brakes would not have an effect.

All these tests were carried out on either Normal or sports tyres; however sucahyo (who carries out a lot of brake tests on GT2) asked if the extra grip of the Racing tyres would enough to make the standard brakes insufficent for the grip avaliable and therefore make the racing brakes worthwhile.

I ran a series of 100mph to 0mph brake tests, twelve runs on each of the five racing tyres, six of the runs with the racing brakes fitted and six without. The average of the runs is then used for comparison. The car used is a stock (apart from the tyres and brakes) BMW M3.

Its also worth noting that all the figures below should be viewed with a margin of error in mind, a speed difference of 1mph can mean a 0.2 meter difference in stoppin distance, and while I am quite happy with the figures an acceptable margin of error would be around 0.1 meter.


R5 Racing Tyres

Without Racing Brakes = 52.4m
With Racing Brakes = 51.5m

Difference = 0.9m


R4 Racing Tyres

Without Racing Brakes = 56m
With Racing Brakes = 55.3m

Difference = 0.7m


R3 Racing Tyres

Without Racing Brakes = 59.1m
With Racing Brakes = 58.6m

Difference = 0.5m


R2 Racing Tyres

Without Racing Brakes = 62.8m
With Racing Brakes = 62.6m

Difference = 0.2m


R1 Racing Tyres

Without Racing Brakes = 67.9m
With Racing Brakes = 67.9m

Difference = 0.0m



Conclusion

Well quite a different set of results from the previous tests, it does appear that the additional grip of some of the racing tyres does warrent the use of racing brakes.

Now the above tests would indicate that a benifit can be seen on tyres of R2 or softer compound, the R1 - super hard tyres showing no difference at all. However the advantages are small until you get to R3 tyres or softer and it should also be remembered that a small margin of error will always exist in these tests and that the results are only indicative for this car.

So an amendment to the racing brakes don't have effect statement, its now 'Racing Brakes may have an effect, but only if you are running racing tyres and even then it depends on the compound you are using.

My recomendation, don't bother with the Racing Brakes unless you are running racing tyres and even then it may depend on the compound you are running.


Regards

Scaff
 
Scaff
My recomendation, don't bother with the Racing Brakes unless you are running racing tyres and even then it may depend on the compound you are running.

Regards

Scaff
What a test 👍, averaging many trial .............
So, racing brakes do increase braking force.
This just makes me more curious, what if we use the racing brakes on ice or dirt or in a surface where the wheel locked easier (wet?). Do using the racing brakes make the braking worse? Do we have to reduce or increase both brake bias? Changing the BBC balance? Seeing that you already have done very many exhausting test, answer from what you know is enough for me :). I am not asking you to take another exhausting test ..........

BTW, what tire in BMW that smoke first, front or rear?
Do the smoke comes at the different speed or different density when using different tire?
Or no smoke at all on all R tire?
Do you think we need to change the brake balance to incorporate the traction of different tire to make the best braking?
 
sucahyo
What a test 👍, averaging many trial .............
So, racing brakes do increase braking force.
This just makes me more curious, what if we use the racing brakes on ice or dirt or in a surface where the wheel locked easier (wet?). Do using the racing brakes make the braking worse? Do we have to reduce or increase both brake bias? Changing the BBC balance? Seeing that you already have done very many exhausting test, answer from what you know is enough for me :). I am not asking you to take another exhausting test ..........

BTW, what tire in BMW that smoke first, front or rear?
Do the smoke comes at the different speed or different density when using different tire?
Or no smoke at all on all R tire?
Do you think we need to change the brake balance to incorporate the traction of different tire to make the best braking?

Thanks for the feedback, I always use averages on my tests, normally the average of six runs, just to make sure that the results are consistent.

Youre observations with regard to ice and dirt are correct, the ower traction surface will cause the tyres to lock sooner. Racing brakes in GT4 seem to have little difference in these conditions, however you are right that they can cause problems in the real world.

Which is why as you again, correctly observe, that both brakeforce and balance would need to be changed and set-up as required.

The actualy main 'real world' benefits of uprated brakes are generally better modulation, feel and resistance to fade.

Hope that helps

Regards

Scaff
 
sucahyo
Thanks :),
How about the M3 tire smoke, do they increase when using stickier tire?

Sorry for the delay in getting back to you, but I had to do a few more runs to check this for you , as I always drive with the 'in-car' view and the data logger means I don't look at many replays when testing.

Not a bit of smoke with any of them, down to the tyres grip and GT4's ABS I guess.

Regards

Scaff
 
Scaff
Not a bit of smoke with any of them, down to the tyres grip and GT4's ABS I guess.

Regards

Scaff
Oh, I see. I ask because in GT2 the stickier tire will make more smoke. In stage 3 turbo BMW 328Ci with no weight mods:
White: hard slick
Red : super soft slick
The weight transfer and BBC is optimize to not smoking the front tire above 50kmph when using hard tire to show the most effect. I use 15/24 BBC, using 24/24 will make both car smoke the front tire for about the same time.



It seems the ABS in GT2 work intermittently (periodical smoke).
 
VIPFREAK
Sorry to interupt but does your guys tests relate to lessening the really bad understeer?
On M3? if my understanding about weight transfer is correct then:
acceleration understeer can be reduced by slippier tire or lower ride height or harder spring rate.
braking understeer can be reduce by stickier tire or higher ride height or lower spring rate or more rear bias brake balance controller.

So, If the problem is exist on acceleration you can try using lower ride height and harder spring rate (lower the damper).
If the problem is exist on braking try to increase the rear BBC and reducing the front BBC.
 
VIPFREAK
Sorry to interupt but does your guys tests relate to lessening the really bad understeer?

On what car and under what conditions?

I would generally not use the BBC as a first line in reducing understeer, we have more than enough suspension tuning to dial in or out understeer. I would recomend setting the BBC to optomise braking stability.

Regards

Scaff
 
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